Normal fetal weight: 2900 gm
Moore KL, Persaud TVN. 1998. The Developing Human: Clinically Oriented Embryology. 6th ed. Philadelphia: WB Saunders Co.
Alveoli mature; new alveoli continue to be formed up to 8 years post-natally.
Duration: 4 weeks
Larsen WJ. 1997. Human Embryology. New York: Churchill Livingstone Inc.